This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-285139, filed Oct. 6, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a probing method and a probing apparatus, and more specifically, to a probing method and a probing apparatus with high reliability, in which a load applied to a main chuck carrying an object of inspection thereon by probes is measured when the main chuck is overdriven to the probes, so that a steady load can always be applied to the main chuck in accordance with the measured value.
As shown in FIG. 8, a probing apparatus 10 for checking integrated circuits on a wafer for electrical properties, for example, is provided with a loading chamber 11, probing chamber 12, controller 13, and display unit 14. In the loading chamber 11, wafers W stored in a cassette C are delivered one after another and transported to the probing chamber 12. The probing chamber 12 adjoins the loading chamber 11. Integrated circuits formed on each wafer W that is transported from the loading chamber 11 are inspected in the probing chamber 12. The controller 13 controls the chambers 11 and 12. The display unit 14 doubles as a control panel for operating the controller 13.
The loading chamber 11 is provided with a pair of tweezers 15 for use as a transportation mechanism for the wafers W. The tweezers 15 moves back and forth in the horizontal direction and rotates forward and reversely, thereby delivering the wafers W in the cassette C one after another and transporting them into the probing chamber 12. A sub-chuck 16 for pre-aligning each wafer W is provided near the tweezers 15. As the sub-chuck 16 receives each wafer W from the tweezers 15 and rotates in the forward direction and the reverse direction in a xcex8-direction, it pre-aligns the wafer W on the basis of its orientation flat.
The probing chamber 12 is provided with a main chuck 17 that carriers each wafer W thereon. The main chuck 17 is moved in X- and Y-directions by means of X- and Y-stages 18, 19, respectively, and moved in Z- and xcex8-directions by means of built-in drive mechanisms. Alignment means 20 is provided in the probing chamber 12. The alignment means 20 serves to align each wafer W with the probes. The alignment means 20 includes an alignment bridge 22 having first image-pickup means (e.g., CCD camera) 21 for imaging the wafer W a pair of guide rails 23 for guiding the bridge 22 in reciprocation in the Y-direction, and second image-pickup means (e.g., CCD camera, not shown) attached to the main chuck 17. A probe card is provided on the top surface of the probing chamber 12. On the upper surface of the probe card, a test head is connected electrically to the card by means of a connecting ring. A test signal from a tester 34 (see FIG. 1) is transmitted to the probe card via the test head and the connecting ring, and further transmitted from the probe card to the wafer W. The object of inspection is checked for electrical properties in accordance with the test signal.
In inspecting the integrated circuits formed on each wafer W, the tweezers 15 takes out one of the wafers W from the cassette C. While the wafer W is being transported to the probing chamber 12, it is pre-aligned on the sub-chuck 16. Thereafter, the tweezers 15 delivers the wafer W to the main chuck 17 in the probing chamber 12. The alignment bridge 22 moves to the center of the probe card. The main chuck 17 moves to the position under the first image-pickup means 21 of the bridge 22, and the wafer on the chuck 17 is aligned with the probe card by means of the first image-pickup means 21 and the second image-pickup means. As the main chuck 17 moves in the X- and Y-directions, the wafer W is subjected to index feed. As the chuck 17 ascends in the Z-direction, the electrodes of the integrated circuits are brought into contact with probes. When the main chuck 17 is overdriven, the integrated circuits on the wafer W are checked for electrical properties with their electrodes electrically in contact with the probes.
In the case of a wafer W with a diameter of 200 mm or less, as shown in FIG. 9A, the wafer W on the main chuck 17 ascends from the position indicated by dashed line to the position indicated by full line as the main chuck 17 is overdriven. As indicated by full line in FIG. 9A, the wafer w rises in the Z-direction without substantially tilting from its horizontal position. As this is done, each probe 24A of a probe card 24 is elastically raised from the position of dashed line to the position of full line of FIG. 9A. The tip of the probe 24A moves from a starting point S to an ending point E, as indicated by thick line. The plane distance covered by the tip that moves from the starting point S to the ending point E, as indicated by hatched arrow in FIG. 9B, is within the area of an electrode pad P of each integrated circuit. Thus, the probe 24A and the electrode pad P are brought electrically into contact with each other, whereupon the integrated circuit is inspected.
In the case of a wafer W with a diameter of 300 mm, the wafer size is too large, and besides, the integrated circuits are hyperfine, and electrode pads are arranged at narrow pitches. The number of pins of the probe card is increased (e.g., to 2,000) correspondingly. A load from about 2,000 probes 24A that acts on the main chuck 17 when the chuck is overdriven is as heavy as, for example, more than 10 kg to 20 kg. Accordingly, an unbalanced load that is generated when the wafer w is overdriven from the position indicated by dashed line in FIG. 10A so that it touches the probes 24A causes the rotating shaft (not shown) of the main chuck 17 to bend. In consequence, the wafer W is tilted for about 20 to 30 xcexcm, for example, as indicated by full line in FIG. 10A, and deflected outward from its original raised position. As this is done, the tip of each probe 24A is elastically raised from the position indicated by dashed line to the position indicated by full line of FIG. 10A, and moves along a track (indicated by thick line in FIG. 10A) that is longer than the one shown in FIG. 9A. Although the starting point S of the tip is situated in the same position as the one shown in FIG. 9A, the ending point E is located outside the area of the electrode pad P, as indicated by hatched arrow in FIG. 10B. Thus, test signals cannot be transmitted from the probes 24A to the electrode pads P, so that the reliability of the inspection is lowered.
In Jpn. Pat. Appln. KOKAI Publication No. 11-30651, the inventor hereof proposed a probing method and a probing apparatus in which dislocation of probes attributable to contact load is corrected three-dimensionally. According to this technique, the probes estimate a distortion of a main chuck in the position where the probes are in contact with a wafer, in accordance with known data, such as information (outside diameter, material, etc.) on the main chuck, information (outside diameter, number of chips, etc.) on the wafer, and information (probe tip area, number of probes, etc.) on a probe card. Based on the estimated value, the position where the probes are in contact with the wafer is corrected three-dimensionally.
According to the probing method and the probing apparatus described in Jpn. Pat. Appln. KOKAI Publication No. 11-30651, a load (needle pressure) in the contact position of the probes is estimated in accordance with the contact position for overdrive operation and a given overdrive, the distortion of the main chuck is estimated according to the estimated load, and the contact position of the probes is three-dimensionally corrected in accordance with the estimated distortion. If the estimated load and an actual load are inconsistent, therefore, the three-dimensional correction of the contact position of the probes may possibly be wrong. Further, the conventional probing method and apparatus use a mechanism that obtains the given overdrive by driving the Z-axis. On the other hand, the distance between the probe tip and the wafer w changes due to deformation of the probe card with time or thermal expansion or contraction of the card during inspection. Since the overdrive of the main chuck is fixed, however, a constant contact load cannot be obtained.
The object of the present invention is to solve the above problems.
An object of the present invention is to bring probes and electrode pads of an object of inspection accurately into contact with one another under a steady load even if a probe card is deformed from various causes or expanded or contracted by any thermal effect.
Another object of the invention is to provide a probing method and a probing apparatus, in which probes and electrode pads of an object of inspection can be brought accurately into contact with one another if a main chuck is tilted by an unbalanced load during overdrive operation, so that high-accuracy inspection can be enjoyed.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
In a first aspect of the present invention, there is provided a probing method comprising steps of: moving a main chuck to align an object of inspection on the main chuck with probes of a probe card located over the main chuck; moving the main chuck toward the probe card, thereby bringing electrodes of the object of inspection into contact with the probes; overdriving the main chuck toward the probe card while measuring a load applied to the object of inspection by contact with the probes and controlling the movement of the main chuck in accordance with the measured load; and inspecting electrical properties of the object of inspection by means of the probe.
Preferably, in this probing method, the control of the movement of the main chuck is control of an overdrive based on the measured load, such that the load has a given value.
Preferably, in this probing method, the control of the movement of the main chuck further includes steps of obtaining a distortion of the main chuck in accordance with the measured load and correcting at least one of dislocations between the object of inspection and the probe in X-, Y-, and xcex8-directions in accordance with the distortion.
Preferably, in this probing method, the measurement of the load applied to the object of inspection by contact with the probes includes steps of locating a polishing mechanism right under the probes, the polishing mechanism including a polish plate to be used to polish the tip of the probes; moving the located polishing mechanism toward the probe card, thereby bringing the polish plate into contact with the probes; overdriving the polishing mechanism toward the probe card; and measuring a load applied to the polish plate by the probes by means of a pressure sensor attached to the polishing mechanism during the overdrive operation.
In a second aspect of the present invention, there is provided a probing method comprising steps of: moving a main chuck in X-, Y-, and xcex8-directions to align an object of inspection on the main chuck with probes of a probe card located over the main chuck; moving the main chuck in a Z-direction, thereby bringing electrodes of the object of inspection into contact with the probes; overdriving the main chuck toward the probe card while measuring a load applied to the object of inspection by contact with the probes by means of a sensor and controlling the movement of the main chuck in accordance with the measured load; and inspecting electrical properties of the object of inspection by means of the probes.
Preferably, in this probing method, the sensor is located on at least one of the lower part of the main chuck and between an LM guide and an XY-stage on which the main chuck is set.
Preferably, in this probing method, the control of the movement of the main chuck is control of an overdrive of the main chuck.
Preferably, in this probing method, the control of the movement of the main chuck includes steps of obtaining a distortion of the main chuck in accordance with the measured load and correcting at least one of dislocations between the object of inspection and the probes in the X-, Y-, and xcex8-directions in accordance with the distortion.
In a third aspect of the invention, there is provided a probing method in which a main chuck is moved in X-, Y-, and xcex8-directions to align an object of inspection on the main chuck with probes of a probe card located over the main chuck, the main chuck is moved in a Z-direction so that electrodes of the object of inspection are brought into contact with the probes, the main chuck is overdriven toward the probe card, and electrical properties of the object of inspection are inspected by means of the probes, the probing method comprising steps of: locating a polishing mechanism right under the probes, the polishing mechanism including a polish plate to be used to polish the tip of the probes; moving the located polishing mechanism toward the probe card, thereby bringing the polish plate into contact with the probes; overdriving the polishing mechanism toward the probe card; measuring a load applied to the polish plate by the probes by means of a pressure sensor during the overdrive operation; and controlling the movement of the main chuck in accordance with the measured load.
Preferably, in this probing method, the sensor is set on the polishing mechanism.
Preferably, in this probing method, the control of the movement of the main chuck is control of an overdrive of the main chuck.
Preferably, this probing method comprises steps of obtaining a distortion of the main chuck in accordance with the measured load and correcting at least one of dislocations between the object of inspection and the probes in the X-, Y-, and xcex8-directions in accordance with the distortion.
Preferably, in this probing method, the control of the overdrive of the main chuck includes steps of obtaining a distortion of the polish plate in accordance with the relation between the load applied to the polish plate and the distortion of the polish plate and the load applied to the polish plate and measured by means of the pressure sensor; obtaining the spring constant of the probes from the distortion and an overdrive of the polish plate; obtaining the spring constant of the main chuck in accordance with the spring constant of the probes and the relation between the load and a distortion of the main chuck; obtaining a load applied to the main chuck by the probes in accordance with the spring constant of the main chuck and the relation between the spring constant and the overdrive of the main chuck; and controlling the overdrive of the main chuck in accordance with the obtained load.
Preferably, this probing method further comprises steps of obtaining a distortion of the main chuck in accordance with the load measured:by means of the pressure sensor and correcting dislocations between the object of inspection and the probe in X- and Y-directions in accordance with the distortion.
In a fourth aspect of the invention, there is provided a probing apparatus comprising: a main chuck carrying an object of inspection thereon; a probe card having a plurality of probes and located over the main chuck; a drive mechanism for moving the main chuck in X-, Y-, Z-, and xcex8-directions; a pressure sensor adapted to measure a load applied to the object of inspection by the probes when the drive mechanism moves the main chuck toward the probe card so that the object of inspection on the main chuck is brought into contact with probes; and a controller for controlling the movement of the main chuck in accordance with a position where the probes touches the object of inspection and the load measured by means of the pressure sensor.
In a fifth aspect of the invention, there is provided a probing apparatus comprising: a main chuck carrying an object of inspection thereon; a probe card having a plurality of probes and located over the main chuck; a drive mechanism for moving the main chuck in X-, Y-, Z-, and xcex8-directions; a pressure sensor adapted to measure a load applied to the object of inspection by the probes when the drive mechanism moves the main chuck toward the probe card so that the object of inspection on the main chuck is brought into contact a probes; and a controller for obtaining a distortion of the main chuck in accordance with a position where the probes touches the object of inspection and the load measured by means of the pressure sensor.
Preferably, the controller of this probing apparatus controls an overdrive in accordance with the measured load so that the load has a given value.
Preferably, the controller of this probing apparatus corrects at least one of dislocations between the object of inspection and the probes in the X-, Y-, and xcex8-directions in accordance with the distortion.
In a sixth aspect of the invention, there is provided a probing apparatus comprising: a main chuck carrying an object of inspection thereon; a polishing mechanism having a polish plate and attached to the main chuck; a probe card having a plurality of probes and located over the main chuck; a drive mechanism for moving the main chuck in X-, Y-, Z-, and xcex8-directions; a pressure sensor adapted to measure a load applied to the polish plate of the polishing mechanism attached to the main chuck by the probes when the drive mechanism moves the main chuck toward the probe card so that the polish plate is brought into contact with probes; and a controller for controlling the drive mechanism, the controller including a mechanism for obtaining the spring constant of the probes in accordance with the load measured by means of the pressure sensor, obtaining the spring constant of the stage in accordance with the relation between the load and a distortion of the main chuck, and obtaining a load applied in the position where the probes touch the main chuck in accordance with the relation between the respective spring constants of the probes and the main chuck and an overdrive of the main chuck.